Conventional military revolver guns such as the M 39 20 mm self-powered revolver gun rely on a gas actuated piston to move an elongated cam which engages a series of cam followers attached to the revolver cylinder. Some revolver gun designs use a full parabolic cam with spring loaded cam followers and others use "half-cams" and a switch mechanism to select different cam followers during recoil and counter-recoil.
Also, the typical revolver gun fires conventionally shaped ammunition, with the typical revolver cylinder chamber including the profile of the ammunition case and a short forward section of reduced straight bore diameter to accommodate the projectile of the round. When the normal revolver gun is fired, the projectile travels the short distance of straight bore at the forward end of the revolver chamber before it "jumps the gap" and enters the actual barrel. The hot, burning propellant gasses follow the base of the projectile and "wash" on the straight bore section of the revolver chamber. At sustained firing rates, the revolver cylinder gets very hot because of this gas wash with serious potential for causing premature detonation of rounds, referred to as "cook-off". To maintain barrel gas pressure and projectile velocity, as well as to avoid undesirable emission of large amounts of barrel gasses at the revolver cylinder, in the typical revolver gun the gap between the revolver cylinder and the rear end face of the barrel must be sealed by a separate delicate component that causes extra machining expense, extra maintenance and can be troublesome operationally.
The geometry of normal revolver guns is such that a fired conventional ammunition case must be extracted out the rear of the revolver chamber and be clear of the area before significant rotation of the revolver cylinder is possible. For high firing rates the conventional revolver gun relies upon high velocity ejection and high velocity ramming of new rounds into the revolver chambers by complex mechanisms responsive to the gas actuated piston and associated operating rod and cams. Further, the typical revolver gun requires high velocity charging to initially load the revolver cylinder in preparation for firing, a further complication.
In the past few years there has been increasing interest in the advantages offered by cylindrically cased telescoped ammunition rounds, and various gun mechanisms have been proposed for firing such rounds: See, for example, the gun mechanism shown in U.S. Pat. No. 4,791,851. However, so far as is known, revolver guns have not been adapted to the use of cylindrically cased telescoped ammunition rounds, except by the present invention. Although they provide significant advantages, such telescoped ammunition rounds require gentler handling by the gun mechanism than do conventional rounds.
In accordance with the present invention, a self-powered revolver gun is provided which is lighter weight, significantly less complex, more reliable, and capable of higher sustained firing rates than a conventional revolver gun while also having the advantage of firing telescoped ammunition rounds.
Also, the gun design, according to the present invention, provides a revolver gun having considerable advantages in various applications as compared to present conventional machine guns which fire conventional ammunition of the same caliber.
For example, by comparison with a Browning M2 HB (0.50 CAL) Machine Gun, a corresponding revolver gun of the present design firing the same caliber projectiles in cylindrically cased telescoped ammunition, is much more compact, much lighter weight, has a significantly higher rate of fire, an equal or higher muzzle velocity and about one-third fewer parts. Moreover, there is a large reduction in ammunition weight for the same number of ammunition rounds. These factors can be very significant for guns mounted on helicopters, for example.
For general reference, a cylindrical, plastic cased telescoped ammunition round is disclosed in U.S. Pat. No. 4,770,098.